Obstruction within a person's upper air passageway may be life threatening. If the obstruction is substantially complete some action to remove or to bypass the obstruction must be taken within three to four minutes or the person will die. Obstruction can occur for many reasons one of which is edema of the pharynx. The pharynx has a soft inner tissue to which body liquids can gravitate to cause edema. Edema can be caused by neck trauma, surgery in the region of the upper air passages, allergic reactions or bleeding in regions near the pharynx, among other causes. When the upper air passage is blocked a person's life may be saved by installing an endotracheal tube, however the swollen pharyngeal area makes it very difficult to pass a tube through the pharynx and impossible to see the part of the larynx through which the tube must pass.
To install an endotracheal tube in an emergency situation it is almost always necessary to have a laryngoscope and some means for illuminating the area of the larynx into which the endotracheal tube must be inserted. A laryngoscope normally has a long blade connected through a hinge-like mechanism to a handle. The handle usually contains batteries and some illumination source which is directed toward the area at the end of the laryngoscope blade. A light source frequently is an incandescent bulb electrically connected to the batteries in the handle. Alternatively, illumination can be provided by sources in the handle that shine into the end of a fiberoptic bundle which passes down the blade to provide illumination at its tip.
Laryngoscope blades come in many shapes. Most of them are elongated blades having a trough-shaped cross section while others are tubular or have a tubular shape with a slit in the tube along one side. Other laryngoscopes have curved blades which follow the shape of the air passageway from a person's mouth to the larynx. Examples of blades of these types can be found in U.S. Pat. Nos. 4,295,465 to Racz; 4,337,761 to Upsher and 3,856,001 to Phillips.
It has been found that when the pharynx suffers serious edema, the tissue is so soft and swollen that it will conform to the shape of the laryngoscope blade. The swollen pharynx will fill the trough of an open blade and will enter any slits or other openings of a partially closed tubular blade. The swollen pharynx thereby not only obstructs the ability to view the larynx directly but it also interferes with the ability to illuminate the area of the larynx.
Tubular blades are available which can displace edematous pharyngeal tissue. Unfortunately existing tubular blades are difficult to use in emergency situations because a patient's jaw and teeth restrict the amount of manipulation that can be performed with a continuous tubular blade. In addition, it is difficult to manipulate instruments or tubes within the long, restricted tubular passageway. Tubular blades are generally used with heavy light sources which are not easily transported and thus not available in emergency situations. Thus, none of the known laryngoscope blades has been found to be satisfactory in dealing with airway emergencies caused by pharyngeal edema.